On this page
NARS2
asparaginyl-tRNA synthetase 2, mitochondrial
NARS2 is located on the long (q) arm of chromosome 11, at band 11q14.1. Arm ratio per GRCh38 - banding schematic.
Explore chromosome 11 in the library →Available at Jeen Health
Clinical tests that include this
Overview
NARS2 encodes asparaginyl-tRNA synthetase 2, a mitochondrial aminoacyl-tRNA synthetase responsible for charging transfer RNA molecules with the amino acid asparagine. This process represents an essential early step in mitochondrial protein synthesis, which produces the protein components of the oxidative phosphorylation machinery responsible for cellular energy generation. The enzyme ensures accurate translation of the mitochondrial genetic code by maintaining fidelity during amino acid incorporation.
Pathogenic variants in NARS2 disrupt mitochondrial protein synthesis, leading to impaired energy metabolism particularly in tissues with high metabolic demands such as the brain and nervous system. The resulting mitochondrial dysfunction typically manifests during infancy or early childhood with neurological features including developmental delay, seizures, and progressive neurodegeneration. Understanding NARS2 function provides insight into the fundamental mechanisms sustaining cellular energy homeostasis and the pathophysiology of inherited mitochondrial disorders.
What the gene does
The NARS2 protein functions as an aminoacyl-tRNA synthetase specifically operating within the mitochondrial matrix compartment. Aminoacyl-tRNA synthetases catalyse a two-step reaction that first activates an amino acid using ATP, then transfers the activated amino acid to the corresponding transfer RNA molecule. For NARS2, this process specifically involves asparagine and its cognate mitochondrial tRNA.
This charging reaction ensures that mitochondrial ribosomes receive appropriately loaded tRNA molecules for accurate protein synthesis. Since mitochondria encode thirteen essential oxidative phosphorylation subunits in their own genome, disruption of this aminoacylation process compromises the synthesis of respiratory chain complexes. The enzyme must discriminate between asparagine and structurally similar amino acids whilst maintaining high catalytic efficiency to support the continuous protein synthesis demands of metabolically active cells.
The NARS2 enzyme belongs to the class II aminoacyl-tRNA synthetase family, distinguished by their characteristic catalytic domain architecture and approach to substrate recognition. Proper NARS2 function requires coordinated recognition of both the amino acid substrate and specific structural features of mitochondrial tRNA molecules, ensuring translation accuracy and maintaining mitochondrial proteome integrity across diverse cellular conditions.
Video: Genetics 101
Chromosome location
NARS2 resides on chromosome 11 at cytogenetic band 11q14.1, positioned on the long arm of the chromosome. This chromosomal region contains numerous genes involved in metabolic and developmental processes. The genomic organisation and regulatory elements controlling NARS2 expression ensure the enzyme is produced at appropriate levels to meet mitochondrial protein synthesis demands across different tissue types and developmental stages.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Pathogenic variants in NARS2 typically result in reduced enzyme activity or protein instability, impairing mitochondrial protein synthesis. The spectrum of reported variants includes missense changes affecting catalytic function and variants predicted to disrupt protein folding or stability. Individual variants may exhibit different effects on enzyme kinetics, thermal stability, or tRNA binding affinity, contributing to variability in clinical presentation and disease severity among affected individuals.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.1236C>G | p.Tyr412Ter | Pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 24 |
c.418C>T | p.Arg140Ter | Pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 24 |
c.563_564del | p.Asp187_Ser188insTer | Pathogenic/Likely pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 24 |
c.727C>T | p.Arg243Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Hearing loss, autosomal recessive 94 |
c.947del | p.Asn316fs | Pathogenic/Likely pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 24 |
c.951C>T | p.Asn317= | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.969T>A | p.Tyr323Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 24 |
c.228del | p.Ala77fs | Pathogenic | ★☆☆☆ | not provided |
c.893_894del | p.Cys298fs | Pathogenic | ★☆☆☆ | not provided |
c.947dup | p.Asn316fs | Pathogenic | ★☆☆☆ | Combined oxidative phosphorylation defect type 24 |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Variants in NARS2 cause rare mitochondrial disorders characterised predominantly by neurological features. Affected individuals typically present in infancy or early childhood with developmental delay, intellectual disability, seizures, and progressive neurological decline. Some individuals exhibit additional features including sensorineural hearing loss, optic atrophy, or metabolic abnormalities. The clinical spectrum reflects the sensitivity of the developing and mature nervous system to impaired mitochondrial energy metabolism, with phenotypic variability influenced by residual enzyme activity and tissue-specific metabolic demands.
No disease links recorded for this gene in our reference set.
UK clinical status
NARS2 appears on multiple NHS Genomic Medicine Service gene panels as a green-rated gene, indicating strong evidence for clinical validity in the specified conditions. The gene features on the DDG2P panel, the Early onset or syndromic epilepsy panel (R59), the Likely inborn error of metabolism panel (R98), the Mitochondrial disorders panel, the Possible mitochondrial disorder - nuclear genes panel (R63), and the Undiagnosed metabolic disorders panel. This multi-panel inclusion reflects the gene's established role in mitochondrial disease and the broad phenotypic spectrum observed in affected individuals, supporting its use in diagnostic genomic testing pathways for patients presenting with relevant clinical features.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What inheritance pattern is associated with NARS2 variants?
Pathogenic variants in NARS2 are inherited in an autosomal recessive pattern, meaning an affected individual typically inherits one altered copy from each parent. Parents who each carry one pathogenic variant are generally unaffected carriers.
How do NARS2 variants cause mitochondrial disease?
NARS2 variants impair the enzyme's ability to attach asparagine to mitochondrial transfer RNA molecules, disrupting mitochondrial protein synthesis. This prevents mitochondria from producing essential components of the respiratory chain, compromising cellular energy generation particularly in metabolically demanding tissues such as the brain.
Can NARS2-related conditions be detected through genetic testing?
Yes, pathogenic variants in NARS2 can be identified through genomic sequencing approaches including targeted gene panels for mitochondrial disorders or comprehensive genome sequencing. Genetic testing is typically pursued when clinical features and biochemical findings suggest an inherited mitochondrial disorder.